Apparatus for tension-calendering fabric



July 17, 1956 w. J. SECREST APPARATUS FOR TENSION-CALENDERING FABRIC 2 Sheets-Sheet 1 Filed Dec.

INVENTOR. Z/ZZZfi/Y Jiiffii'f July 17, 1956 w. J. sEcREs-r 2,

APPARATUS FOR TENSION-CALENDERING FABRIC Filed Dec. 22, 1952 2 Sheets-Sheet 2 IN V EN TOR. I MAY J-iflfi'if BY%MZ I United States Patent APPARATUS FOR TEN SIGN -CALEN DERING FABRIC William J. Secrest, Cuyahoga Falls, Ohio, assignor to The Firestone Tire & Rubber Company, Akron, Ohio, a corporation of Ohio Continuation of application Serial No. 97,766, June 8, gggfigsg'This application December 22, 1952, Serial No.

6 Claims. (Cl. 1541.75)

This invention relates to the incorporation of cord tire fabric, or a plurality of separate closely spaced cords, commonly known as weftless cord fabric, in a rubber sheet although in certain respects it has use in connection with rubberizing other forms of fabric or material, and relates more particularly to means to impart a uniform tension to the warp cords of the fabric.

This application is a continuation of the parent application Serial No. 97,766, filed June 8, 1949, now U. S. Patent No. 2,627,296.

Pneumatic rubber tires commonly include a number of superimposed relatively thin plies of rubberized cords composed of cotton, rayon, nylon or other material. The cords are ordinarily rubberized by one or more passes between the rolls of a rubber calender or calenders whereby softened rubber compound is formed into a sheet about the cords. Before calendering, but preparatory thereto, the cords are usually in a woven fabric roll supported in a stock rack near a calender. It is to be understood, however, that instead of being in fabric rolls the separate cords may be led to the calender from stock rolls mounted in a creel. After calendering, the sheet of rubberized cords is usually wound with a separating liner into a roll on suitable take-off stock shells mounted on a driven shaft.

The prior art had furnished tensioning devices such as (1) a friction hand-brake on a fabric let-off roll said hand-brake adaptable only for manual control, (2) a roll immediately in front of the feed side of the calender equipped either with a friction brake or linked to the calender drive by a system of drive chains and sprockets to rotate at a slower speed than the calender rolls, (3) a compensator located between two calenders and putting tension on the passing fabric by means of suspended weights on a dancer roll.

The prior art tensioning devices are deficient in two respects (1) each tensioning device was adaptable only to local control and not to integration into a system of overall uniform tension synchronization (2) these friction devices are not susceptible to accurate adjustment, require high maintenance because of friction and heat build-up, and for this reason tensions in run after run of stock cannot be reproduced by reproducing settings of the friction brake hand-wheel. These deficiencies were not critical when only slow speed, low tension calendering was practiced. However, with the advent of high speed-high tension calendering these deficienc1es have become critical. For example in a tandem calender arrangement where uniform tension is necessary for a uniform end product the prior art tension devices, not being adaptable to overall synchronization, can apply tension only at local points with no overall uniformity over the length of passing material. Also, attempts to rubberize fabric at low tension with high calender roll pressures result in crushed and wrinkled fabric. These results are, of course, undesirable.

The variations in the tension to which the cords are subjected in their rubberizing operation results in the cords at low tension being flattened into an elliptical eross-sectional shape as the cords are squeezed between calender rolls. The flattening of the cords reduces the available space between the cords into which rubber may flow. After the pressure on the cords is released the cords return, at least partially, to their original round shape which leaves the space between the cords not completely filled with rubber. Since before the present invention only relatively low tensions were possible, the fault of flattening the cords was always present. Heretofore, a calender operator has had to be alert to use the maximum roll pressure without extreme flattening of the cords and/ or causing the cords to back up into a wrinkle and become crushed. The higher tension on the cords made possible by the present invention makes possible greatly improved calendering since at the time the rubber is pressed about the cords, they have their maximum spacing and are taut and firm, thus resisting backing up and flattening, and providing somewhat shallower and wider spaces between the cords into which the rubber more readily flows and completely fills.

Therefore, the art of rubberizing tire fabric by calendering prior to the present invention had developed to the point where it had been found desirable to increase greatly both the speed of calendering and the tension placed on the individual fabric cords as they pass through the rubberizing calender. Increased speed is desirable to cut production costs in View of increased labor costs While increased tension allows increased calender roll pressures and is desirable to make a rubberized tire fabric of greater strength. The prior art did not supply apparatus capable of rubberizing fabric at high speeds and high tension.

An object of the invention is to provide means for placing cord tire strain members, to be rubberized by calendering, under predetermined equal tensions in their passage through a calender.

Another object is to subject the individual warp cords of tire fabric, whether Weftless or not, to more uniform tension during a rubberizing operation than has been possible heretofore.

A further object is to pass tire fabric through a calender for rubberizing under tension sufficient to prevent wrinkling of the fabric immediately in front of the calender rolls.

Another object is to subject the cords of tire fabric to higher and constant longitudinal tension during calendering, than has been practical heretofore.

Another object is to provide rubber calender tension means including regenerative braking whereby a substantial amount of the energy expended in creating the tension is returned to the line.

Another object is to provide means for applying a predetermined uniform tension to tire fabric on the feed side of a rubber calender independent of the fabric roll.

Another object is to provide means adapted to subject each cord of tire fabric to substantially the same longitudinal tension whereby the cords of the tire will be more equally stressed in service.

Another object of the invention is to provide apparatus adapted to apply uniform tension at various stations to continuously moving fabric material.

Further objects and advantages will be apparent from the following description of the invention, reference being had to the accompanying drawings, wherein:

Fig. l is a diagrammatic view in perspective of apparatus and material employed in calendering tire cord fabric in accordance with the present invention;

Fig. 2 is a fragmentary sectional view taken in the plane indicated by the lines 22 of Fig. 1 illustrating the crimp in the warp cords as the fabric is unwound from a roll and before it has been subjected to substantial longitudinal tension;

Fig. 3 is a fragmentary view taken in the plane indicated by the lines 33 of Fig. 2 showing the position of the filling or pick threads relative to the Warp when the warp is free of tension;

Fig. 4 is a fragmentary sectional view taken in the plane indicated by the lines 4-4 of Fig. 1 illustrating the manner in which the crimp in the warp threads shown in Fig. 2 straightens out under longitudinal tension;

Fig. 5 is a fragmentary sectional view taken in the plane indicated by the lines 5-5 of Fig. 4 illustrating the crimp which occurs in the filling threads shown in Fig. 3 when the warp threads are placed under tension;

Fig. 6 is a fragmentary sectional view taken in the plane indicated by the lines 6-6 of Fig. 1 showing the relative position of rubber and warp threads after the first calender pass;

Fig. 7 is a fragmentary sectional view taken in the plane indicated by the lines 7-7 of Fig. 1 showing the relative position of rubber and cords after the second and final calender pass; and

Fig. 8 is a wiring diagram showing the means by which the various tension devices act in cooperation due to the synchronization by a centrally located compensator.

The present invention solves the problem of applying uniform high tension to continuous fabric being rubberized by providing a series of tension stations along the path of travel of such fabric. The tension stations are synchronized to apply uniform tension by the monitoring of fabric tension by one of such stations to which the other stations are responsive. This invention is made possible by two novel subcombinations to be described hereinafter i. e. a drag generator tension device and a compressed air controlled compensator.

Referring to Fig. 1 in detail it will be seen that there is shown diagrammatically the principal elements employed in a continuous calendering operation of cord tire fabric. These elements in the order of their occurrence are a roll 10 of bare cord 5, idler rollers 11 and 12 and a rubber covered tension roll 13 the latter being connected to a drag generator 14 by means of a shaft 9 to comprise drag generator tension device 111; top, middle and bottom rolls 15, 16, and 17 respectively, of a threeroll rubber calender 102; a bank of rubber 18 between rolls and 16, a calendered sheet of rubber 19 on the surface of roll 16, idler rolls 20 and 21, compensator generally indicated at 108 comprised of dancer roll 22, sprocket wheels 29a and 30a, air cylinders and 26, piston rods 27 and 28, sprocket chains 29 and 30; idler roller 31, a tension roll 32 connected to a drag generator 33 by means of shaft 8 to comprise drag generator tension device 112; the top, middle and bottom rolls 34, 35, and 36 respectively, of a second rubber calender 109, a bank of rubber 37 between the rolls 34 and of said second calender, a coat of rubber 38 on roll 35, tension roll 39 and tension motor 110, a series of cooling drums 40, 41, 42, 43, 44 and 45, drum being driven by a motor 46 through the medium of chain 47, a roll 48 driven by a motor 49 through the medium of a shaft 7; a stock take-off roll 50 driven by a motor 51 through the medium of a shaft 6, a roll 52 of liner from which a liner 53 is unwound and with the rubberized fabric is wound into a roll 50. Alternate take-off means are usually provided and such means are shown in broken lines wherein 54 is the stock take-off roll. Roll 54 is driven by motor 55 through the medium of a shaft 4. A liner roll 56, from which a liner 57 is drawn and with the rubberized fabric is wound into roll 54. It is to be understood that the elements enumerated above are retained in the usual supports which for the purpose of clarity in describing the invention are not shown.

The drag generator 14 is mechanically associated with the motor 106 of the calender, see Fig. 8, so that said generator is immediately responsive to changes in speed of the calender. Tension on the drag generator 14 may be set by a hand rheostat, not shown, at the start of the rubberizing operation and such tension will remain uniform on the tension roll 13 at all speeds of the calendering operation. The drag generator 14 is responsive to changes in calender speed and by use of the hand rheostat identical tension may be set for run after run or varied as production specifications require. This reproducibility factor makes a drag generator tension device such as 111 adaptable to tensioning different styles and grades of fabrics.

The drag generator tension device is but a subcombination which makes possible applicants broader inventive combination. As applied to a tandem calender arrangement this combination lies in a first calender 102 associated with the first drag generator tension device 111, the tension compensator generally indicated at 108 between said first calender and the second calender 109, the second calender 109 associated with the second drag generator tension device 112 and the tension roll 39 and motor 110 on the discharge side of a calender 109.

In the combination just described the fabric passes over the drag generator tension device 111, through the first calender 102, over the tension compensator 108, over the second tension device 112, through the second calender 109, over the tension roll 39, cooling drums 40, 41, 42, 43, 44, 45 and is wound into a liner on a take-01f roll 51. Along the line of flow of fabric there are then four tension stations aforementioned, first drag generator tension device 111, compensator 108, second drag generator tension device 112, and the tension roll 39. These four tension stations act in cooperation to maintain a uniform tension over the entire length of the fabric by responding to the monitoring of the compensator in the manner to be described.

The compensator 108 includes a dancer roll 22 rotat ably mounted on a rod 3 the ends of which are attached to sprocket chains 29 and 30 passing over sprockets 29a and 30a mounted on the opposite ends of a bar 23. The ends of the sprocket chains are each attached to piston rods 27 and 28 connected to pistons in cylinders 25 and 26. The dancer roll 22 operates two rheostats and 100a controlling respectively calender motors 106 and 107 so that vertical movements of the dancer roll 22 will be reflected through rheostats 100 and 100a in changes in calender speed.

To commence a fabric rubberizing operation the desired tensions are set by the calender operator at the two drag generator tension devices 111 and 112 and the tension roll 39 by setting hand rheostats such as rheostat 86 Fig. 8. As Will be explained later, the drag generators 1.4 and 33 are controlled by control units identical to the unit controlling generator 39, which is fully shown in Fig. 8. The air cylinders 25 and 26 of the compensator are charged with air pressure from an air line, not shown, to place the dancer roll 22 against the fabric to achieve the desired tension. The calenders are than started to commence the rubberizing operation.

The fabric moving through the rubberizing system is initially under uniform tension because the drag generator devices 111 and 112 as well as tension roll 39 are set for the same tension by hand rheostats and the compensator air cylinders 25 and 26 are set at the same tension. However, either calender may slow down because lower plasticity rubber is being fed into it, or either calender may speed up because of high plasticity rubber being fed into it. Also, variations in stretch may occur in different sections of the fabric. These variations and other factors would normally destroy the uniformity of tension application at the four tension stations. However, the compensator 108 solves this problem by synchronizing the tension at all stations. This is accomplished because the dancer roll 22 initially is pulled against the passing fabric to provide the desired tension thereon by the compressed air in the air cylinders 25 and 26. Fluctuations in tension on the passing fabric cause the dancer roll 22 to rise or fall thereby operating the two rheostats 100 and 1 a to vary correspondingly calender motor speeds. The drag generator tension devices 111 and 112 and the tension rolls 39 and 13, being responsive to the calender motor speeds, are thereby slowed down or speeded up to bring the tension of the fabric at all four tension stations back to uniformity. In other words, the compensator coordinates all tension stations by monitoring the tension of the passing fabric and synchronizing the calender motors accordingly.

Referring to Fig. 8 a diagrammatic view of the mechanical-electrical combination of the broad invention is shown. Calenders 102 and 109 are driven by electric calender motors 1% and 107 which are in turn energized by generators 113 and 114-. Generators 113 and 114 are responsive to settings of rheostats 100 and 100a which are in turn responsive to the vertical movements of dancer roll 22. Since the vertical movements of dancer roll 22 are sensitive to changes in tension in the passing fabric, the speeds of calender motors 106 and 107 are governed by said tension changes.

The drag generators 14, 33 as well as the tension motor 110 are mechanically linked to the calender motors 106 and 107 respectively. The wiring of the tension stations 111 and 112 including generators 14 and 33 are similar to the wiring of tension station 120 including tension generator 110. For simplicity, therefore, only the wiring associated with tension motor 110 is shown and described but it is to be understood that the wiring of the drag generators with the corresponding calenders is similar.

Calender motor 107 is associated through a well known arrangement of tach generator 115, auxiliary generator 116, regulator 117 and booster 118 with tension motor 110. A hand rheostat 86 is arranged to vary through well known electrical means the current supplied to motor 110.

Adjustments of hand rheostat 86 set the motor speed of tension motor 110 and thereby the tension which roll 39 puts on the fabric. After the initial tension setting of the hand rheostat 86 at the start of the run and when the fabric is passing through the system, fluctuations in tension of the fabric cause dancer roll 22 to rise or fall manipulating rheostat 100a which in turn slows down or.

speeds up calender motor 107. Motor 107 is mechanically linked to tach generator 115 which through generator 116, regulator 117 and booster 118 drives tension motor 110. Roll 39 being driven by motor 110 puts tension on the fabric coming from calender 109 in response to the speed of calender motor 107. As mentioned above, once the calender operator sets the hand rheostat controlling each tension motor to produce a given tension it will remain at that value, both at high and low speeds of the fabric travel and even during accelerating or decelerating periods. It will be understood that the use of a drag generator such as the generator 14 results in returning a substantial portion of energy into the power system.

In addition to control of the tension motor 111 by hand rheostat 86 this motor is controlled by the calender motor 107 which in turn is regulated by dancer roll rheostat 100a. As the dancer roll 22 manipulates the dancer rheostat 100, the speed of the calender is varied and thereby the tension motor 14, being responsive to changes in speed of the calender motor, regulates the tension of the passing fabric.

Following one common practice in operating a rubber calender, the first calender in this system including rolls 15, 16 and 17 are operated by feeding rubber, which has been broken down on a mill or otherwise caused to become warm and soft, into the bite of rolls and 16, where the rubber forms a bank 18. The opening between rolls 15 and 16 is such as to permit a layer or coat of rubber 19 to pass therethrough and to travel on the surface of roll 16 toward and onto one side of fabric 5 as it passes between rolls 16 and 17. Rolls 16 and 17 are spaced apart suflicient distance to permit the fabric 5 to pass therebetween and to cause the fabric to be squeezed between the rubber coat and the rolls whereby the rubber is forced upon and about the cords of the fabric 5.

During the first calender pass the ultimate position the cords will occupy in the completed rubber sheet is established and it will be seen that at this point the position the cords will occupy relative to each other, the amount of crimp remaining in the cords, the amount the cords have been reduced in diameter due to tension, the spacing between the cords and the tension to which the cords have been subjected relative to each other is established. In the case of .034 gauge cotton cords, usually a .010" of rubber coating is laid upon and forced in and about the cords, this rubber being referred to in the industry as a skim coat. One practice is to press this coat upon the cords with rolls 16 and 17 traveling at even surface speeds. It will be noted that in the first calender pass that the rubber has been placed on one side of the fabric as will be seen by reference to Fig. 6. In practicing the present invention, the tension applied to the fabric is extremely high as compared to tensions used heretofore. This is made possible by the positive control provided through the medium of the tension motor acting as a drag generator which is sensitive to the changes applied of the calender motor. However, in the present invention there must be a relation between the tension on the fabric between rolls 13 and the first calender and the tension on the fabric as it leaves the first calender. In the present case the tensions on the fabric on both sides of the first calender roll 17 are equal, a tension of 2500 pounds on each side has been found to be satisfactory in calendering cotton cord fabric. It is to be understood, of course, that the tensions may be increased or decreased, or varied relative to each other if found desirable.

In either bank or straight skimming there must be a substantial pressure placed on the rubber between rolls 16 and 17 and rolls 35 and 36. This squeeze distorts the rubber and causes some of it to move away from the pressure or toward the oncoming fabric. Heretofore when the tension on the fabric from roll 10 was dependent on the resistance to its pull set up by the roll of fabric itself, said pull. being created solely by the rotation of calender rolls 16 and 17 between which the fabric was squeezed, it often happened that either all the fabric or certain cords thereof, did not have sufiicient tension to resist the backtlow or movement of rubber, with the result that the fabric would wrinkle or buckle just before passing into the bite of the calender rolls. When this occurred the fabric would become crushed by the calender rolls and often so badly that the cords would be completely severed. Such crushing resulted in serious material loss and the calender operator was confronted with the problem of regulating the squeeze so as to get the maximum pressure of the rolls on the fabric and rubber without causing the wrinkling or buckling of the fabric just described.

The greater the squeeze the better rubber impregnation of the fabric, however, to obtain the best results the ideal fabric tension relative to a given squeeze of the rubber and fabric between the calender rolls should be given the fabric. This means in practice that, for example, as roll 17 is raised toward roll 16 increasing the squeeze of rubber and fabric passing between these rolls that the tension on the fabric 5 should be and in fact must be, increased until these two forces, squeeze and tension, are in proper balance, as observed by the calender operator. Since high tension on fabric 5 has been used heretofore it was only possible to subject such skim to a relatively light squeeze. The light squeeze resulted in very limited penetration of rubber between the cords of the fabric and it is an important feature of the present invention to make possible improved penetration of rubber at this first calender pass. Since the amount of tension placed upon fabric is controlled by means of a manually operated rheostat it will be seen that the said balance between squeeze and tension may be definitely and conveniently maintained.

Tension controls other than mechanical brakes had been supplied by the prior art but these controls were too cumbersome to cooperate in a synchronized system wherein independent tension stations along the line of travel of fabric had to have high and uniform tension.

Controlled tension on the feed and outlet side of the calender makes possible higher tensions than could he used heretofore. High tensions result in taut cords having reduced diameters and accordingly increased spacing therebetween at the point the fabric is passing between the calender rolls. This facilitates the forcing of the rubber between and about the cords.

By reference to Fig. 6 it will be seen that the rubber coat placed upon the fabric by the first calender pass substantially fills the space between the cords, it being noted that there is a tendency for the rubber to draw back somewhat after the fabric has passed from between rolls 16 and 17.

The invention produces a novel and useful result on the fabric being rubberized. The uncoated fabric between roll 1% and tension roll i3 is either free or substantially free of tension and accordingly has approximately the same crimp in the warp as when woven. This will be seen by reference to Fig. 2 wherein the relative positions of tensioniree warp cords 76, 71 and filling threads 72 are shown. Cords 7t) and 71 are to become the strain members of a cord tire and they are retained in sideby-side relation by the filling threads. If they are cotton cords they may be, for example, .034 gauge and have a count of 26 ends to the inch. If they were rayon they would probably be .029 gauge and have a count of 29 ends to the inch. Size of cord, count, etc., may be changed, and nylon, rayon, wire or strain members of other materials found satisfactory may be substitutcd for the cotton cords discussed here in detail. The filling threads 72 perform no useful function after the fabric is rubberized. Before rubberizing, the filling threads serve only to make possible the handling of the strain or warp members in the form of fabric as compared to handling each cord in a separate spool. As will be seen in Figs. 2 and 3 the ailing is substantially free of crimp prior to the application of longitudinal tension on the warp cords 70 and 71. In this condition the filling threads bear lightly against the warp.

It will be seen by reference to Figs. 4 and 5 that the tension applied to the uncoated fabric between tension roll 13 and the first calender has substantially removed the crimp from the warp and in doing so has crimped the filling threads. The removal of the crimp from the warp insures the complete burial of these cords in the sheet of rubber.

It is to be understood that the invention contemplates the handling of fabric that has been previously treated as in the case of certain dipping treatments of rayon cords before rubberizing or so-called gum dipped cotton cords. it is also to be understood that the invention may be used in a similar manner as set out hereinabove to equalize and impart the amount of tension desired in cords before they are delivered to a rubber calender. The same is true in a textile mill to impart predetermined tensions to cords before they are wound into rolls.

The invention is adapted for operation with a four roll calender, or calenders of any type or arrangement, and it is to be understood that it is not to be limited to the specific details of construction described above and shown in the accompanying drawing, or to the particular sequence of method steps, since many modifications will readily occur to one skilled in the art from a considerationof this disclosure. The invention includes all modifications coming within the scope of the appended claims and their equivalents.

I claim:

1. A combination for processing sheet material under constantly uniform tension along its entire length comprising two rubber calenders arranged in tandem, a fabric tensioning device disposed on the delivery side of each calender, each said tensioning device comprising rolls over which said sheet material passes in frictional contact, a drag generator at each tensioning device having a driving connection with one of said rolls, a pneumatic compensator between said ealenders, said compensator having a roll held by pneumatic pressure against said sheet material and adapted to apply a constant force normal to the pianc thereof, a first rheostat and a second rheostat, said first rheostat responsive to movement of said compensator roll toward said sheet and said second rheostat responsive to movement of said compensator roll away from said sheet, said drag generators electrically connected to said rheostats and responsive thereto whereby action and reaction of said sheet against the constant force applied by said compensator roll controls the amount of tension placed upon said sheet by said tensioning devices.

2. A combination for processing sheet material under constantly uniform tension along its entire length comprising two rubber calenders arranged in tandem, electric motors in driving connection with said calenders, a fabric tensioning device disposed at the delivery side of each calender, each said tensioning device comprising rolls over which said sheet material passes in frictional contact, a drag generator at each tensioning device having a driving connection with one of said rolls, a compensator having a roll held against said sheet material and adapted to apply a constant force normal to the plane thereof, a rheostat responsive to movement of said compensator roll toward and away from said sheet, said drag generators and said electric motors electrically connected to said rheostat and responsive thereto whereby action and reaction of said sheet against the constant force applied by said compensator roll actuate said drag generators and said electric motors thereby controlling the amount of tension placed upon said sheet.

3. A combination of apparatus for maintaining traveling continuous, sheet material under constant uniform tension along its length, comprising a let-off roll for paying out said sheet material and a wind-up roll for collecting said payed-out sheet material, a drag generator at each roll having driving connections each therewith, a compensator intermediate said let-off roll and said wind-up roll having means held against said sheet material by a constant force, two rheostats responsive to movement of said compensator means in relation to said sheet material, said drag generators electrically connected to each said rheostat and responsive thereto whereby action and reaction from said sheet against the constant force applied by said compensator means controls the amount of tension placed upon said sheet by said let-oil and wind-up roll.

4. A combination of apparatus for maintaining traveling continuous, sheet material under constant uniform tension along its length comprising a let-off roll for paying out said sheet material and a wind-up roll for collecting said payed-out sheet material, a train of material processing apparatus over which said sheet material passes located between said let-off roll and said wind-up roll, at least two tension stations having rolls over which said material passes between said let-off roll and said wind-up roll and adapted to apply tension to said passing sheet material, a drag generator at each said tension station having driving connection with said tension roll, a compensator intermediate said let-off roll and said wind-up roll having means held against said sheet material by a constant force, at least two rheostats responsive to movement of said compensator means in relation to said sheet material, each said drag generators electrically connected to a rheostat and responsive thereto whereby action and reaction from said sheet against the constant force applied by said compensator means controls the amount of tension placed upon said sheet by said let-ofi and said wind-up rolls.

5. A combination of apparatus for processing sheet material under constantly uniform tension along its entire length comprising a let-off roll and a wind-up roll, at least one calender intermediate said let-oft roll and said wind-up roll and adapted to receive and process said sheet material, tensioning devices disposed along the path of travel of said sheet material between said let-01f roll and said wind-up roll, each said tensioning device comprising a roll over which said sheet material passes in frictional contact, a drag generator at each tensioning device having a driving connection with one of said tensioning rolls, at least one of said tensioning devices responsive to the speed of the calender, a compensator intermediate said let-off roll and said wind-up roll having a means held against said sheet material by a constant force, rheostats responsive to the movement of said compensator in relation to said sheet material, said drag generators electrically connected to said rheostats and responsive thereto whereby the action and reaction from changes in tension in said sheet against the constant force applied by said compensator roll controls the speed of the calender and the amount of tension placed upon said sheet material by said tension devices.

6. A combination of apparatus for maintaining traveling continuous, sheet material under constant uniform tension along its length comprising a let-E roll for paying out said sheet material and a wind-up roll for collecting said payed-out sheet material, a train of material processing apparatus over which sheet material passes located between said let-off roll and said wind-up roll, at least two tension stations having rolls over which said material passes between said let-off roll and said wind-up roll and adapted to apply tension to said passing sheet material, a drag generator at each said tension station having driving connection with said tension roll, a compensator intermediate said let-off roll and said wind-up roll having a roll held against said sheet material by a constant pneumatic force, at least two rheostats responsive to movement of said compensator roll in relation to said sheet material, each said drag generators electrically connected to a rheostat and responsive thereto whereby action and reaction from said sheet against the constant force applied by said compensator roll controls the amount of tension placed upon said sheet by said let-off and said wind-up rolls.

References Cited in the file of this patent UNITED STATES PATENTS 1,500,232 Castricum July 8, 1924 1,500,234 Castricum July 8, 1924 1,509,365 Midgley Sept. 23, 1924 1,824,593 Castricum et al. Sept. 22, 1931 2,082,816 Adams et al. June 8, 1937 2,195,009 Lessman et a1 Mar. 26, 1940 2,340,067 Lessmann Jan. 25, 1944 2,433,014 Rendel Dec. 23, 1947 2,445,866 Wilson et al July 27, 1948 2,627,296 Secrest Feb. 3, 1953 

1. A COMBINATION OF PROCESSING SHEET MATERIAL UNDER CONSTANTLY UNIFORM TENSION ALONG ITS ENTIRE LENGTH COMPRISING TWO RUBBER CALENDERS ARRANGED IN TANDEM, A FABRIC TENSIONING DEVICE DISPOSED ON THE DELIVERY SIDE OF EACH CALENDER, EACH SAID TENSIONING DEVICE COMPRISING ROLLS OVER WHICH SAID SHEET MATERIAL PASSES IN FRICTIONAL CONTACT; A DRAG GENERATOR AT EACH TENSIONING DEVICE HAVING A DRIVING CONNECTION WITH ONE OF SAID ROLLS, A PNEUMATIC COMPENSATOR BETWEEN SAID CALENDERS, SAID COMPENSATOR HAVING A ROLL HELD BY PNEUMATIC PRESSURE AGAINST SAID SHEET MATERIAL AND ADAPTED TO APPLY A CONSTANT FORCE NORMAL TO THE PLANE THEREOF, A FIRST RHEOSTAT AND A SECOND 